The invention relates generally to an article engagable and retainable about a threaded shaft, and more specifically to a low profile, self locking unitary nut having a relatively consistent torque performance with a reduced statistical spread over several repeated cycles of nut installation and nut removal about the threaded shaft.
Lock nuts with a threaded bore engagable about a threaded shaft have many configurations and applications. There exists for example a variety of lock nuts having gaps arranged transversely to the bore axis or gaps arranged radially to the bore axis and proximate one end portion of the nut. The gaps are narrowed by deformation of the nut to misalign the threads in an effort to provide means for retaining the nut in tight engagement about the shaft. Nut retention performance however is often diminished substantially upon removal of the nut from the shaft resulting from a tendency of the gap or gaps to widen as the nut is thread about the shaft during installation and removal. This adverse effect on retention performance is particularly significant after the first installation and continues to worsen as the nut is subject to repeated cycles of installation and removal, which may be necessary for cleaning or maintenance. In practice, a large torque is generally required for the first installation of the nut about the shaft in comparison to a substantially reduced torque required for subsequent removal and installations, which is indicative of the compromise in nut retention performance. These prior art nuts do not provide optimum retention performance, have low retention performance after removal from the shaft, and have a relatively inconsistent torque performance with a large statistical spread, which often fails to comply with industry established torque specifications.
Others have endeavored to improve nut retention performance. U.S. Pat. No. 815,541 to Leatherman for example discusses a nut lock having opposing U-shape members disposed about a threaded bore wherein the U-shape members are formed by a combination of slots arranged transversely and radially to the bore axis. A median portion of each U-shape member is connected to the nut by a corresponding neck, and the end portions of the U-shape members are inwardly bent toward the bore axis to provide tight engagement with the shaft. This nut however lacks optimum retention performance, has low retention performance after removal from the shaft, and has a relatively inconsistent torque performance with a large statistical spread, which often fails to comply with industry established torque specifications.
U.S. Pat. No. 2,213,353 to Whitcombe discusses a lock nut having opposing U-shape members formed in a cylindrical extension of the nut. The trailing end portion of each U-shape member is downwardly bent, and one or more end portions are inwardly bent toward the bore axis for nut retention. Whitcombe however teaches away from downwardly bending the leading end portion of each U-shaped member to prevent cross threading during installation. In addition, the cylindrical extension disposed on the nut of Whitcombe adversely increases the profile of the nut thereby limiting its use in applications that require a low profile. This nut also lacks optimum retention performance, has low retention performance after removal from the shaft, and has a relatively inconsistent torque performance with a large statistical spread, which often fails to comply with industry established torque specifications.
In view of the discussion above, there exists a demonstrated need for an advancement in the art of retaining a threaded member about a threaded shaft.
It is therefore an object of the invention to provide a novel article engagable and retainable about a threaded shaft that overcomes problems in the prior art.
It is also an object of the invention to provide a novel article engagable and retainable about a threaded shaft that is economical, reusable and provides improved torque performance.
It is another object of the invention to provide a novel article engagable and retainable about a threaded shaft wherein the article has a reduced first on torque.
It is a further object of the invention to provide a novel article engagable and retainable about a threaded shaft wherein the article has a relatively consistent torque performance with reduced statistical spread over several nut installation and removal cycles.
It is a further object of the invention to provide a novel article engagable and retainable about a threaded shaft wherein the article has an improved torque performance that meets an established torque specification.
Accordingly, the present invention is drawn to a novel article having a body member engagable and retainable about a threaded shaft wherein the body member, which in one embodiment is a tool engagable nut, includes a first end, an opposing second end, and a threaded bore with a bore axis for receiving the threaded shaft. A plurality of resilient posts extend along the body member wherein each resilient post is inclined inwardly toward the bore axis to provide a prevailing torque on a threaded shaft disposed in the threaded bore. A pair of resilient arms with end portions extend from each resilient post wherein each pair of resilient arms is inclined downwardly toward the body member to provide a prevailing torque on a threaded shaft disposed in the threaded bore. The resilient posts and resilient arms contribute to retaining the body member about the threaded shaft. The prevailing torque nut has a relatively low first installation torque and a relatively consistent torque performance with reduced statistical spread over several nut installation and removal cycles within an established torque specification. The lock nut preferably is a unitary member formed of a metal material.
These and other objects, features and advantages of the present invention will become more fully apparent upon consideration of the following Detailed Description of the Invention with the accompanying drawings, which may have disproportionate dimensions for ease of understanding, wherein like structure and steps are referenced by corresponding numerals and indicators.